Here's my take on this issue. Sorry if it's unpopular. My go-to LFS dips all of my corals real quick out the door. To me, it doesn't mean that they assume that all of their for-sale corals are carrying parasites. On the contrary. The frag sales tanks as a whole look very good. I assume they dip incoming corals as well. I've never asked, but I think I might.
But lets face it. You're local LFS is a retailer. They are bringing in corals from wholesalers, aqua culturists, and local reefers. Their livelihood depends on receiving and selling livestock. They can't possibly know what's coming in on every coral. To expect any LFS to quarantine every coral shipment or trade for 72 days before sale is completely unrealistic in my mind. Dipping corals as they leave the shop is simply an added measure of safety for the customer. Bravo!
I have my own coral dipping regime (I don't quarantine corals). Not everyone does. When I see the LFS dipping corals out the door, it means to me that maybe they could be helping a customer possibly not have to deal with a pest that could otherwise cause a problem. It's definitely not a guarantee, but it sure don't hurt.